Flexible pipe with an associated end-fitting

ABSTRACT

An assembly of an end-fitting ( 9 ) and a flexible pressure pipe which is of a non-bonded structure and comprises a number of layers including at least one layer having a number of helically wound flat metallic tensile armor wires with end parts which, in the assembled condition, are embedded in an anchor consisting of a casting material such as epoxy which is injected into a cavity formed in the end-fitting. The flat wire end parts have at least one twist turning generally around the centerline of the wire. Said twists lock the tensile armor wires firmly in the anchor and therefore provide a greater resistance to axial tensile loads acting on the assembly than has been known before. Furthermore the joint is a simple and cheap structure and can be made in situ.

BACKGROUND ART

The invention concerns a flexible pressure pipe with an associatedend-fitting having an axially extending through opening, where the pipeis of a non-bonded structure comprising a number of layers including anextruded polymer inner lining extending into the through opening.

Flexible pressure pipes are used for a variety of applications,including water supply lines, sewage lines and lines for transportingchemicals such as liquid ammonia and phosphoric acid and also highpressure offshore flexible pipes for the oil and gas industry.

The joint between the inner lining and the end-fitting must be able toresist the axial tensile load acting on the inner lining, when theflexible pipe is descending over a great length, and also such stresseswhich arise as a consequence of temperature fluctuations.

Conventionally, said joint is provided by squeezing the inner liningbetween an outer conical ring and an inner conical ring which is pressedin between the inner lining and the carcass of the pipe. The effect ofthis squeezing will, however, diminish gradually as the plasticizerdisappears from the plastic material of the lining.

Another drawback is that temperature stresses can arise in the jointbecause the plastic material has a high coefficient of expansion.

In the document GB 891 611 A is described a tamber-proof fitting forattachment to the end of a hose having a liner of substantially plasticmaterial with a braided covering thereon. By assembling, an end of theliner is squeezed between an inner nipple and an outer body memberhaving, on the innerside, sharp ribs which by the squeezing is forcedinto the material of the liner forming complementary share grooves inthe liner. This known technique cannot be used for pipes having an innercarcass which not allows the liner to be squeezed and the nipple to bescrewed in. Furthermore, the share grooves in the liner functions with adangerous notch effect which is not acceptable for high-quality flexiblepressure pipes exposed to high loads.

SUMMARY OF THE INVENTION

The object of the invention is to provide a flexible pressure pipe withan associated end-fitting of the type mentioned in the opening paragraphin which the joint between the inner lining of the pipe and theend-fitting is a simple and cheap structure and provides a greaterresistance to axial tensile loads acting on the inner lining than hasbeen known before.

This is achieved in that on the outer surface of the end part of theinner lining at least one annular groove is formed, a lock ring isattached to the inner lining by means engaging said annular groove, andthe lock ring is attached to the end-fitting, whereby the inner liningcan be firmly connected to the end-fitting in a simple and timeefficient manner.

The lock ring can be attached to the annular groove in the inner liningby a substantially corresponding annular rib on the inner surface of thelock ring. This embodiment is very simple.

To compensate for inevitable tolerances of the inner lining and in thepreparation of the joint between the lining and the lock ring, inanother expedient embodiment the lock ring can be attached to theannular groove in the inner lining by a circlip which is fitted intoboth said annular groove in the inner lining and an opposing groove inthe inner surface of the lock ring.

A particularly strong connection between the inner lining and the lockring is obtained when the annular groove in the outer surface of theinner lining is formed by rolling, such that the material of the liningwill be strengthened and imparted with a better structure by coldhardening.

For improving the strength of the joint between the lock ring and theinner lining, the annular groove in the outer surface thereof can beformed as a segment of circle and the depth of the groove can be between0.2-0.5 times the thickness of the lining.

The lock ring can easily be mounted on the inner lining when it has atransverse slit or consists of two or more sectors of a circle.

In a particularly advantageous and strong embodiment, the lock ring canbe fitted into a holding groove formed in the wall of the throughopening of the end-fitting, and for securing this connection between thelock ring and the holding groove there may be a gap filled with acasting material, e.g. a polymer such as epoxy.

The invention also concerns a method for assembling a flexible pressurepipe with an associated end-fitting having an axially extending throughopening, where the pipe is of a non-bonded structure comprising of anumber of layers including an extruded polymer inner lining extendinginto the through opening. Said method comprises: removing the layerssurrounding the lining at the end of the pipe, rolling at least oneannular groove in the outer surface of the end part of the inner lining,placing a lock ring consisting of two or more sectors of a circle aroundthe end part of the lining such that a rib on the lock ring, or acirclip which engages a groove in the lock ring, engages the grooverolled in the outer surface of the end part of the lining, securing thelock ring sectors, and attaching the lock ring to the end-fitting. Themethod can advantageously be performed in situ.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained more fully in the following description,given by way of example, with reference to the drawings, in which:

FIG. 1 shows, partly in axial section, a typical flexible pressure pipe,

FIG. 2 shows, in axial section, an assembly of the flexible pressurepipe shown in FIG. 1 and an end-fitting,

FIG. 3 is a perspective view on an enlarged scale of a part of a firstembodiment of a lock ring mounted on an inner lining of the flexiblepipe shown in FIG. 1, and

FIG. 4 is a perspective view on an enlarged scale of a part of a secondembodiment of a lock ring mounted on an inner lining of the flexiblepipe shown in FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a flexible pressure pipe, which is generally designated by1. The pipe is of a non-bonded structure comprising a number of layerswhich in this embodiment are:

a carcass 2 of an interlocking structure made from metallic strips. Thecarcass serves, in the main, to prevent collapse of the pipe due to pipedecompression, external pressure, tensile armour pressure and mechanicalcrushing loads,

an inner lining 3 in the form of an extruded polymer layer for providinginternal fluid integrity,

a pressure armour 4 in the form of structural layers consisting ofhelically wound C-shaped metallic strips with a high lay angle,

a tensile armour 5 consisting of a pair of helically counter wound flatmetallic tensile wires 6 with a lay angle typically between 20° and 60°.The tensile armour serves to provide resistance to axial tensile loads,and

an outer sheath 7 in the form of an extruded polymer for shielding thestructural elements of the pipe from the outer environment and providingmechanical protection.

FIG. 2 shows an assembly 8 of an end-fitting 9 and the flexible pressurepipe 1. The end-fitting 9 forms the transition between the pipe and theconnector and for this purpose has a first part 10 with a connectionflange 11, a second part 12, and a third part 30. The three parts 10;12; 30 delimit a cavity 13 which partly is substantially cone-shaped.The end-fitting 9 has furthermore a through opening 14 for accommodatingan end of the pipe 1.

When assembling the flexible pressure pipe 1 with the end-fitting 9 theflat metallic wires 6 of the tensile armour 5 are led into the cavity 13in the end-fitting and a casting material, e.g. epoxy, is injected intothe cavity making an anchoring for the wires.

The carcass 2 is fastened to the end-fitting 9 by means of a lock nut15, and to the inner lining 3 by means of a lock ring 16 fitting into anannular groove 17 in the wall of the through opening 14. The lock ring16 is in the embodiment shown secured in the groove 17 by a castingmaterial 18, e.g. epoxy, which is injected through a hole 19.

A ring 20 provides a stop for the lock nut 15. In the embodiment shown asealing ring 21 for tightening the end-fitting 9 and the inner lining 3is fitted into a groove 22 in the ring 20.

After having removed the layers 4, 5, 7 surrounding the lining at theend of the pipe, two annular grooves 23 are rolled in the outer surfaceof the end part of the inner lining, whereafter the lock ring 16, whichconsists of one or more sectors of circle, is placed around said endpart and secured with a clamp 24.

In the embodiment shown in FIG. 3 two annular ribs 25 are formed on theinner surface of the lock ring 26. The ribs 25 correspond to the annulargrooves 23 rolled in the inner lining 3 and therefore engage thesegrooves firmly.

FIG. 4 shows another embodiment of a lock ring 27 according to theinvention. In this case two annular grooves 28 are formed on the innersurface of the lock ring 27 and two circlips 29 simultaneously engagethe grooves 28 formed in the lock ring and the groove 23 rolled in theinner lining 3. This construction can advantageously compensate fortolerances which are caused by the manufacturing of the inner lining andthe lock ring.

Having thus provided a general discussion, and specific illustrations byway of examples it is to be understood that no undue restrictions are tobe imposed by reason thereof. Many other embodiments are imaginablewithin the scope of the invention. The specific locking, according tothe invention, between the inner lining 3 of the flexible pressure pipe1 and the end-fitting 9 can also be used in combination with otherconstructions of the joint between the end-fitting 9 and the tensilearmour wires 6 and the carcass 2, respectively, in addition to thosedescribed above and shown in the figures.

What is claimed is:
 1. A flexible pressure pipe with an associatedend-fitting (9) having an axially extending through opening (14), wherethe pipe is of a non-bonded structure comprising of a number of layersincluding an extruded polymer inner lining (3) extending into thethrough opening, wherein on the outer surface of the end part of theinner lining (3) at least one annular groove (23) is formed, a lock ring(16) is attached to the inner lining (3) by means engaging said annulargroove (23), and the lock ring (16) is attached to the end-fitting (9).2. A flexible pressure pipe according to claim 1, wherein the engagementmeans for attaching the lock ring (16) to the at least one annulargroove (23) in the outer surface of the inner lining (3) consists of agenerally corresponding annular rib (25) on the inner surface of thelock ring (16).
 3. A flexible pressure pipe according to claim 1,wherein the engagement means for attaching the lock ring (16) to the atleast one annular groove (23) in the outer surface of the inner lining(3) consists of an opposing groove (28) in the inner surface of the lockring (16) and a circlip (29) which is fitted into both grooves (23;28).4. A flexible pressure pipe according to claim 1, wherein the at leastone annular groove (23) in the outer surface of the inner lining (3) isformed by rolling.
 5. A flexible pressure pipe according to claim 1,wherein the cross-section of the at least one annular groove (23) in theouter surface of the inner lining (3) is formed substantially as asegment of circle.
 6. A flexible pressure pipe according to claim 1,wherein the depth of the at least one annular groove (23) in the outersurface of the inner lining (3) is between 0.2-0.5 times the thicknessof the lining (3).
 7. A flexible pressure pipe according to claim 1,wherein the lock ring (16) has a transverse slit or consists of two ormore sectors of circle.
 8. A flexible pressure pipe according to claim1, wherein the lock ring (16) is fitted into a holding groove (16) inthe wall of the through opening (14) of the end-fitting (9).
 9. Aflexible pressure pipe according to claim 8, wherein there is a gapbetween the lock ring (16) and the holding groove (17), and that thisgap is filled with a casting material (18), e.g. a polymer such asepoxy.
 10. A method for assembling a flexible pressure pipe with anassociated end-fitting (9) having an axially extending through opening(14), where the pipe is of a non-bonded structure comprising of a numberof layers including an extruded polymer inner lining (3) extending intothe through opening (14), wherein the method comprises, removing thelayers surrounding the lining (3) at an end of the pipe, rolling atleast one annular groove (17) in the outer surface of the end part ofthe inner lining, placing a lock ring (16) consisting of two or moresectors of a circle around the end part of the lining (3) such that arib (25) on the lock ring (16), or a circlip (29) which engages a groove(28) in the lock ring (16), engages the groove (23) rolled in the outersurface of the end part of the lining, securing the lock ring sectors,and attaching the lock ring (16) to the end-fitting (9).